Metal Hydride Hydrogen Compressors are thermal machines based on solid state metal hydride (MH) technology. Their operating principle is based on heat and mass transfer (hydrogen) in the reaction bed during absorption and desorption processes.
Schematic layout of the continuously operating MH compressor
The main part of the MH hydrogen compressor is a container (MH vessel) filled with a hydrogen storage alloy. The container is equipped with a heat exchanger for heat removal in the charge mode and heat supply in the discharge mode.
During charge low pressure hydrogen is absorbed by the alloy to form the metal hydride. The heat produced during absorption reaction is removed by cooling. After finishing the charge stage, the hydrogen-saturated MH is heated that results in hydrogen release at high pressures.
By using of two or more MH vessels, it is possible to arrange continuous hydrogen compression. Cooling / heating of the MH vessels is conducted in the opposite phase, when one MH vessel is cooled absorbing low-pressure hydrogen, the other one is heated desorbing high-pressure hydrogen into the discharge line. After a time period when hydrogen absorption in the first vessel and desorption in the second vessel are completed, the cooling / heating mode is changed to the opposite: the first MH vessel is heated releasing hydrogen, while the second is cooled absorbing hydrogen from the charge line.